[introduce CMake var EXTRA_DFLAGS_LDC for PGO flags]

As DFLAGS_LDC affect the ldc2-unittest executable too, which is built
without optimizations (but with `-g -unittest`).

Author: kinke

.github/actions/2a-build-pgo/action.yml

@@ -22,7 +22,7 @@ runs:
           -DBUILD_SHARED_LIBS=OFF
           "-DCMAKE_C_COMPILER=${{ runner.os != 'Windows' && '$PWD/../clang/bin/clang' || 'clang-cl' }}"
           "-DCMAKE_CXX_COMPILER=${{ runner.os != 'Windows' && '$PWD/../clang/bin/clang++' || 'clang-cl' }}"
-          "-DDFLAGS_LDC=-fprofile-generate -vp-counters-per-site=1.5"
+          "-DEXTRA_DFLAGS_LDC=-fprofile-generate -vp-counters-per-site=1.5"
         extra_d_flags: ${{ inputs.extra_d_flags }}
         extra_cxx_flags: -fprofile-generate -mllvm -vp-counters-per-site=1.5
         lto_mode: ${{ inputs.lto_mode }}

.github/actions/helper-build-ldc/action.yml

@@ -57,7 +57,7 @@ runs:
           cxx_flags+=(-flto="$lto_mode")
         fi
         if [[ "$with_pgo" == true ]]; then
-          flags+="-DDFLAGS_LDC=-fprofile-use=../pgo-ldc/merged.profdata "
+          flags+="-DEXTRA_DFLAGS_LDC=-fprofile-use=../pgo-ldc/merged.profdata "
           cxx_flags+=(-fprofile-use=../pgo-ldc/merged.profdata)
         fi
 

CMakeLists.txt

@@ -137,6 +137,8 @@ set(COMPILE_D_MODULES_SEPARATELY OFF CACHE BOOL "Compile each D module separatel
 
 set(LDC_ENABLE_ASSERTIONS "${LLVM_ENABLE_ASSERTIONS}" CACHE BOOL "Enable LDC assertions. Defaults to the LLVM assertions mode; overriding may cause LDC segfaults!")
 
+set(EXTRA_DFLAGS_LDC "" CACHE STRING "Extra D compiler flags for the ldc2 executable only, e.g., for PGO.")
+
 # Allow user to specify mimalloc.o location, to be linked with `ldc2` only
 set(ALTERNATIVE_MALLOC_O   ""     CACHE STRING "If specified, adds ALTERNATIVE_MALLOC_O object file to LDC link, to override the CRT malloc.")
 
@@ -677,7 +679,7 @@ build_d_executable(
     "${LDC_EXE}"
     "${LDC_EXE_FULL}"
     "${LDC_D_SOURCE_FILES}"
-    "${DFLAGS_BUILD_TYPE} ${DFLAGS_LDC}"
+    "${DFLAGS_BUILD_TYPE} ${DFLAGS_LDC} ${EXTRA_DFLAGS_LDC}"
     "${ALTERNATIVE_MALLOC_O};${LDC_LINKERFLAG_LIST}"
     "${FE_RES}"
     "${LDC_LIB}"